One of the problems in the application of spray paints is control of overspray or drifting of the paint. This is particularly true of solvent based paints. When such paints are applied by spraying, the pressure exerted on the paint is usually at least 15 psig and as the paint passes through the spray nozzle, fine droplets are formed. The droplets become finer as spray pressures are increased. These fine droplets tend to drift or be carried away from the target by wind or convection currents.
The prevention of drift is particularly important in the use of paints for marking center lines in roadways as well as in many other uses where it is undesirable to have the paint spread to a surrounding area. Thus, in many cases where the surrounding area contains vegetation the ordinary oil based paint would destroy the vegetation.